S- to N-Acyl transfer in S-acylcysteine isopeptides via 9-, 10-, 12-, and 13-membered cyclic transition states.

S-Acyl cysteine peptides containing α-, β- or γ-amino acid residues undergo long-range S- to N-acyl transfer to give analogs of native tripeptides and tetrapeptides containing additional carbon atoms in the chain. The ease of intramolecular S → N-acyl transfer relative to intermolecular transacylation is favored increasingly for 9 < 12 < 13 ~ 10-membered cyclic transition states; the observed order is explained on conformational and intermolecular interaction considerations.